The invention relates to a cooling fluid circuit comprising a compressor to bring the fluid in vapour phase from a low pressure to a high pressure, a condenser to bring the high-pressure fluid from the vapour phase to the liquid phase by yielding heat to an external medium, an expansion valve to bring the fluid in liquid phase from high pressure to low pressure, an evaporator to bring the low-pressure fluid from the liquid phase to the vapour phase by receiving heat from an external medium, and first, second, third and fourth ducts to transfer the fluid from the compressor to the condenser, from the condenser to the expansion valve, from the expansion valve to the evaporator and from the evaporator to the compressor respectively.
Fluid circuits of this kind are used in particular in air-conditioning installations for the passenger space of motor vehicles.
In such a circuit, the efficiency of the condenser and of the evaporator is imperfect. The fluid leaving the condenser contains a large fraction of vapour, and that leaving the evaporator contains liquid residue. These imperfections in turn are detrimental to the operation of the expansion valve and of the compressor. The presence of vapour in the fluid arriving at the expansion valve involves a loss of efficiency. The presence of liquid in the fluid arriving at the compressor causes phenomena called liquid and oil knocks.